1. Field of the Invention
The present invention relates to an optical transmission line forming method to form an optical transmission line between optical transmission terminals connected by the optical transmission line to transmit optical signal via the optical transmission line, an apparatus for implementing such method and an optical circuit formed by such method.
2. Description of the Prior Art
Electrical wiring method has been popular as a connecting method of electronic circuits. However, with progress of the processing rate of the circuits in the recent years, electrical wirings cannot realize accurate signal transmission due to signal delay, waveform distortion or the like. For these reasons, a so-called optical interconnection technology has been proposed to transmit signals with an optical transmission line which has been enabled by replacing an electrical signal into an optical signal. However, here rises a problem that mounting and assembling are difficult because the optical interconnection technology requires the accuracy as high as several .mu.m or less for coupling between a light emitting element and a light receiving element or an optical waveguide.
Moreover, as a method of connecting an optical waveguide with a light emitting element, a non-contact type optical coupler has been proposed to perform indirect connection, in place of the direct connection, by propagating the light signal in the space. However, such a non-contact type optical coupler introduces a measure, in order to make small a coupling loss, to process the end part of an optical fiber provided opposed to the light emitting means into a shape of lens but provides more complicated mounting (aligning) process. Since the optical connection between an optical fiber and light emitting and receiving elements of the related art is required to provide the light emitting and receiving surfaces on the upper surface of a die to couple these elements with the light from or to the upper direction, the end part of the optical fiber is cut and polished in the angle of 45 degrees and simultaneous control is also required for rotation of fiber around the optical axis and three axes XY .theta. for axial alignment. As a result, the positioning cost takes the greater part of the mounting cost.
In view of overcoming this problem, the official gazettes of the Japanese Published Unexamined Patent Application Nos. Hei 269903 and 88028 propose the method of optically coupling elements by connecting in direct the optical fiber with an element by the wire bonding method.
However, when an optical semiconductor apparatus of the related art, utilizing an optical fiber to form an optical transmission line between the optical transmission terminals which will become an optical signal transmitting end or receiving end, introduces the mounting method similar to the wire bonding method, if the optical fiber is bent for the purpose of wire bonding, the optical fiber will be broken at this bending area, substantially disabling the connection because the optical fiber does not have such flexibility as freely assuring wire bonding for connection in the length from several .mu.m to several mm. In addition, even if the optical fiber does not break and the wire bonding can be performed, since a shearing stress is always applied to the coupling area between the light emitting element and light receiving element or optical waveguide, here rises such a reliability problem that the coupling area will generate separation of bonding to a considerable extent.